Cycloolefins can be polymerized through the olefin structure to yield polycycloaliphatics, or through a ring-opening process to yield unsaturated linear polymers and copolymers. The latter process has particular appeal since the resulting polymers are sulphur-vulcanizable. Since cyclopentene is a readily available ethylene production by-product, considerable art has focussed on the ring-opening polymerization and copolymerization of cyclopentene. Recent patents and publications have disclosed a number of catalyst systems and polymerization processes for producing desirable polymers and copolymers of cycloolefins. Examples of patents describing catalysts and catalyst combinations as well as processes for polymerizing cycloolefins include U.S. Pat. Nos. 4,002,815; 3,853,830; 3,597,403; and 3,778,420.
A number of the catalyst systems which have been suggested in the prior art for preparing polymers of cyclomonoolefins such as tungsten or molybdenum halides in conjunction with organoaluminum compounds provide linear polymers having a high proportion of gel. More recently, other catalyst systems have been discovered which produce linear polymers of cyclic monoolefins which essentially are gel-free. For example, in U.S. Pat. No. 4,025,708, a solvent is used for the tungsten compound in the catalyst system allowing for improved process control and substantially gel-free cyclopentene homopolymers and copolymers.
Dicyclopentadiene (a norbornene-type monomer) is another readily available ethylene production by-product, but not as much consideration has been given in the prior art to homopolymers and copolymers of dicyclopentadiene. It has been observed that the application of the broad prior art teachings to the preparation of homopolymers and copolymers of dicyclopentadiene generally results in the production of a polymer which is substantially insoluble in hydrocarbon solvents including aliphatic, cycloaliphatic and aromatic hydrocarbons. U.S. Pat. Nos. 3,853,830 and 4,002,815, describe processes for preparing substantially gel-free copolymers of dicyclopentadiene with cyclopentene utilizing a catalyst which comprises (a) at least one compound selected from the group consisting of dialkylaluminum iodides, alkylaluminum diiodides and mixtures of trialkylaluminum compounds with elemental iodine and (b) at least one solvent-soluble or monomer-soluble tungsten compound, and (2) at least one non-conjugated acyclicolefin having at least one hydrogen on each double-bonded carbon atom. Soluble copolymers are obtained when component (a) is charged before catalyst component (b).